Method of coating articles



1'. K1 cox METHODOF'COATING ARTICLES Filed July 12, 1934 FIG. I

.Lllrll Nov. 16, 1937.

7.'K.COX

fi- Tfl M ATTORNEY INVENTOR FIG. 2

Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE METHOD OF COATINGARTICLES Application July 12, 1934, Serial No. 734,711

9Claims.

This invention relates to a composition of matter for use in and amethod of coating articles, and more particularly to a. composition foruse in and a method of coating a metallic wire such as, for example, atinned copper wire with an insulating material whereby the resistance ofthe coating to being stripped from the wire may be given any desiredvalue between wide limits.

An object of the invention is to provide a composition for use in and amethod of forming a coating of a compound on articles wherein as .apreliminary step to the application of the compound, a composition isapplied to the article to enhance or diminish the natural adhesion to 5the article of the subsequently applied coating,

the components ofthe composition being proportioned to have the desiredefiect.

With the above and other objects in view one embodiment of the inventioncomprises a composition consisting principally of two ingredients: onean adhesion resisting substance such as a liquid oil, molten paraiiinwax, or the like; the other an adhesion promoting agent such as formic,acetic, oleic or palmitic acid or the like.

25 The invention is further embodied in a method of coating a wire withinsulating compound which includes the steps of depositing a thincoating or him of the above described composition on the. wire and thenapplying and forming so the insulating compound thereon. The resistanceto stripping from the wire of the finished coating will then depend uponthe relative proportions oi the ingredients of the composition used andcan be predeterminedly varied by varying those 35 proportions.

Other; objects and characteristic features oi! the invention will appearfrom the following detailed description of one embodiment thereof takenin connection with the accompanying drawing in 40 which the samereference numerals are appended to identical parts in the severalfigures and in which- Fi 1 is a broken view in side elevation of adevice for treating with the preliminary compo- 5 sition a wire to besubsequently coated with insulating compound;

Fig. 2 is a similar view of a device for applying and forming a coatingof insulating compound on the treated wire; and

50 Fig. 3 is an enlarged cross section of a treated and coated wire.

As herein disclosed, the invention contemplates a new step in an oldmethod of insulating wire involving the use of a new composition ofmatter.

55 The method may be practised by the use of old and well-knownapparatus, and hence the apparatus is disclosed in the drawing in asemi-diagrammatic and fragmentary manner, the apparatus being no part ofthe invention.

In Fig. 2, element 20 is the coating head of an extrusion coatingmachine, generally indicated at 2!, in which a coating 22 of insulatingcompound may be applied and formed on a wire' 23 passing through thehead. For a detailed description of the construction and operation of an10 apparatus 20, 2| adapted for use in practising the present inventionreference may be had to the specification and drawing of United StatesPatent No. 1,770,969, to George L. Cherry, for a Method of and apparatusfor sheathing cables, issued under date of July 22, 1930.

In order to'control the adhesion of the coating 23 to the wire 22, thewire is given. a novel preliminary treatment in the apparatus of Fig. 1.This apparatus comprises a tank 24 attached to a support 25 and having ahinged cover 26. Preferably the support 25 is some stationary part ofthe machine 2! and the tank 24 and the coating head 20 are located inalignment so that the wire 22 may pass in a straight line first through25 the tank 24 and then through the coating head 2 i The tank 2|contains a liquid bath 2! of the composition which is one of thesubjects of the present invention. The composition comprises essentiallyan oil which tends to diminish the adhesion to the wire of thesubsequently applied insulatlng compound, and an ingredient such asformic, acetic, oleic or palmitic acid, which tends to enhance theadhesion of the compound to the wire. 7

A distributing wheel or roll 28 is mounted to rotate freely in the tankwith its lower portion extending down into the liquid bath and its uppersurface substantially tangential to the path of the wire through thetank. The roll 28 is driven by the friction of the wire thereon andcarries composition up from the bath and deposits it on the wire. Astationary arcuately curved shield 28 may be stationarily mounted at therising side of the roll 28 to prevent excessive splashing.

In operation the wire 23 is drawn by any convenient means not shown,such as a capstan from a. supply not shown, through the tank and incontact with the roll and then through the coating head, emergingtherefrom with a coating 60 of insulating material, which may then bevulcanized, it necessary, in any appropriate apparatus not shown andwhose resistance to being stripped from the wire depends principally onthe relative proportions of oil and acid in the bath.

Thus in one instance the bath conted 87.5% of a well-known mineral oilwidely used as an automobile lubricant and commercially known as600Woil, together with 12.5% of oleic acid; and the insulating compoundconsisted of 25% reclaimed rubber, 20% smoked sheet rubber, 5%

mineral rubber, 5% zinc oxide, 2% sulfur, 2%

pine tar, and 41% whiting.

In this instance the resulting coating adhered to the wire withsuflicient tenacity to permit of handling the wire on the capstans,take-up de vices and similar apparatus used in handling such Wire, whileat the same time thecoating could be cleanly and relatively easilystripped from the wire wherever it was desired to bare the wire, as forsoldering other wire or terminals or the like thereto.

With a higher ratio of oil to acid the insulating coating adheres lesstenaciously to the wire until, if no acid be used at all, there is noadhesion of the coating to the Wire. On the other hand, if theproportion of acid be increased, a point is reached at which the coatingadheres so firmly that the coating will shear within the body thereof ifan attempt be made to strip it, leaving a film of the insulatingmaterial as if welded to the metal.

The molecular mechanics of the processes involved are not clear.However, it would appear that the oil by itself tends to form a film onthe wire preventing contact and hence adhesion of the insulatingcompound to the wire; and that the acid acts on the surface of the wire,etching it to roughness and forming salts. The roughened surface of thewire will tend to promote adhesion mechanically. Also it may well bethat the metallic salts formed migrate more or less into the insulatingcompound and tend to harden the inmost film thereof in and around theroughnesses of the wire.

It has been found that formic, acetic, oleic and palmitic acids arecapable of-produclng the desiredand characteristic efiect while stearicand some other organic acids are not edective. It has also been foundthat any oil, whether of animal, vegetable or mineral origin, which willform a workable solution or emulsion with any one of the above fouracids is efiective. Furthermore a wax such as paraffin war: may be usedif means be provided to heat the tank 2W, such as a steam coil Elli, tokeep the bath molten and liquid.

In the embodiment herein disclosed the invention is shown as applied tothe coating of wire with electrically insulating composition, buttheinvention is not limited to such use only. In fact, it is applicablewherever a compound analogous in character but not necessarily infunction is to be applied to a metallic object, and it is desired tocontrol the tenacity of adhesion of the compound to the article. Theembodiment of the invention herein disclosed is illustrative merely, andmay be widely-modified and departed from in many ways without departingfrom the spirit and scope of the invention, as pointed out in andlimited only by the appended claims. What is claimed is:

l. A composite article comprising a. metallic body, a coating of avulcanized material containmg rubber on said body and an intermediatelayer compounded of a mixture 01 an ingredient tending to promoteadhesion between said body hmh, Edd

gredient tending to resist adhesion between said body and saidvulcanized. material, said second named ingredient being selected from agroup consisting of oils and paraiiln waxes, said adhesion resistingingredient being capable of forming a solution or an emulsion with saidadhesion promoting ingredient, said intermediate layer being in contactwith the metallic body and the vulcanized material containing rubber.

2. An insulated electric conductor comprising a metallic strand, aninsulating coating formed thereover and an intermediate layer compoundedof a homogeneously blended but chemically uncombined mixture of alubricating oil and oleic acid, said oil being capable of forming asolution or an emulsion with said acid, said intermediate layer being incontact with said metallic strand and insulating coating. w

3. The method of insulating an electrical conductor with an insulatingmaterial, which includes depositing upon the conductor a film of amixture of an ingredient tending to resist adhesion between saidconductor and said insulatlng material, said ingredient being selectedfrom a group consisting of oils and paramn waxes, and another ingredienttending to promote adhesion between said conductor and said insulatingmaterial, said second named ingredient being selected iroma groupconsisting of formic, acetic, oleic and palmitic acids, said adhesionresisting ingredient being capable of forming a solution or an emulsionwith said adhesion promotingingreclient, and thereafter forming on saidconductor and film a coating of an insulating material, the

proportions of the adhesion resisting and adhesion promoting ingredientsbeing relatively variable to vary the degree of tenacity of adhesionbetween the conductor and the insulating mate i. The method of coating ametallic article with a vulcanized insulating material containingrubber, which includes the steps of depositing on the article a film ofa mixture of an ingredient tending to resist adhesion between saidmetallic article and said insulating material, said ingredient beingselected from a groupconsisting of oils and paramn-waxes, and anotheringredient,

tending to promote adhesion between said metallic article and saidinsulating material, said sec-- ond named ingredient being selected froma group consisting oi formic, acetic, oleic and palmitic acids, saidadhesion resisting ingredient being capable of forming a solution or anemulsion with said adhesion promoting ingredient, subsequently applyinga coating of a vulcanizable insulating material on said metallic articleand film and thereafter vulcanizing the coating.

5. The method of insulating an electrical conductor with an insulatingmaterial, which includes depositing upon the conductor a film of amixture of a lubricating oil and oleic acid, said oil being capable offorming a solution or an emulsion with said acid, and thereafter formingon said conductor and film a coating of an insulating material, theproportions of the oil and acid being relatively variable to vary thedegree of tenacity of adhesion between the conductor and the insulatingmaterial;

6. The method oi coating a. metallic article with a vulcanizedinsulating material containing rubber, which includes the steps ofdepositing on the article a fllm of a mixture of a lubricating oil andoleic acid, said oil being capable of forming a solution or an emulsionwith said acid, subsequently applying a coating of vulcanizableinsulatingmataialonsaidmetallicarticle and him and thereafterrulcanising coating. 7

ductor with a vulcaniled insulating material, which comprises treatingthe surface of the conductcr with a mixture 0! an ingredient tending toresist adhesion between said conductor and said insulating material,said t being selected from a groupof oils and paraflin waxes, andanother ingredient tending to promote adhesion between said conductorand said insulating material, said second named ingredient beingselected from a group consisting of formic, acetic, oleic and palmiticacids in pro- 7 portions of the order oi 87.5% and 125% respectively,said adhesion ingredient being resist adhesion between said article andsaid coating material, said second named ingredient being selected froma group consisting of oils and paraiiin waxes, said adhesion resistingingredient being capable of forming a solution or an emulsion with saidadhesion promoting ingredient, the ratio of one ingredient to the otherbeing adjusted according to the degree of tenacity of adhesion required.

.9. The method of insulating an electrical conductor with a vulcanizedinsulating material, which comprises treating the surface of theconductor with a mixture of an ingredient tending to resist adhesionbetween said conductor and said insulating material, said. ingredientbeing selected from a group consisting of lubricating oils and paraiilnwaxes, and another ingredient tending to promote adhesion between saidconductor and said insulating material, said second named ingredientbeing selected from a group consisting of iormic, acetic, oleic andpalmitic acids in proportions of the order of 87.5% and 125%respectively, said adhesion resisting in gredient being capable offorming a solution or an emulsion with said adhesion promotingingredient, and thereafter applying a coating of a vulcanizableinsulating material on said conductor.

THOMAS K. COX.

